Thermal dye printers typically use precut dye print receiver media sheets. This is so because rolled receiver paper leave a curl in the finished paper. The current trend in consumer electronics is to produce cheaper, smaller, and lighter products for the consumer market. The emphasis being to develop products that are smaller then those produced in the past. FIG. 1 shows a conventional multi-pass thermal printer layout. The length or footprint of the thermal printer is primarily determined by the configuration of the sheet feed tray to the thermal printer head. The printer requires a paper supply tray and a temporary storage area at least the size of the paper to accommodate the multiple print passes of the print in process. This requirement for a paper supply tray and a temporary storage area adds to the overall length and weight of thermal printers.
U.S. Pat. No's. 4,505,695, 5,533,821, and 5,637,070 disclose sheet decurling mechanisms. They disclose complex mechanical devices having multiple belts and rollers which is subject to frequent mechanical break-downs and their complex designs add to the cost of the thermal printer. Additionally, these arrangements do not accommodate both a forward and reverse direction of the receiver paper.
Arvidson, in U.S. Pat. No. 3,806,574 discloses a method of decurling flat photographic sheets. Arvidson teaches the use of reverse rewinding of rolled sheets to decurl photographic film. The process of winding, rewinding and holding the film does not contemplate the high speeds and rates associated with thermal printing. To apply the process as disclosed by Arvidson would significantly slow-down the page per minute (ppm) requirements of today's consumer.
Green et al. in U.S. Pat. No's. 5,549,864, and 5,580,588 disclose a process for decurling a strip of photosensitive material. The method and apparatus as claimed is to a complex configuration incorporating a series of twists and bends to bring about the desired result. Additionally, U.S. Pat. No. 3,552,668 discloses a curl removing device which uses pressure from a series of rollers to remove the curl. The methods and apparatus as disclosed above are not conducive for multi-pass printing and add size and weight to thermal printers.